The girlfriend and I have been trying to "front-load" the cooking for the week as much as possible, meaning, for instance, we cook a very large portion on Monday, and eat it through Wednesday. Costco has been a god send in this regard.
For instance, we really like the Costco ground turkey as it's a lean protein and serves as a great vehicle for whatever flavors you feel like. It's sold in a 4 pack of ~24oz each for about $15, so it's a great bargain too. We'll usually buy one of those, and a big bag of broccoli florets (about $4).
On Monday, I'll take 2 24oz packs of ground turkey and make a turkey meatloaf - this comes out about 8 6oz servings. I'll also make some steamed rice. So, my prep time on Monday might be about 30min + 1-1.5hrs cook time. However, we can divvy this up into 8 meals (Monday dinner, Tuesday lunch, Tuesday dinner, Wednesday lunch) - 1 6oz portion of meatloaf, some rice, and a cup or so of broccoli (which we just microwave). Granted, they're not the most exciting meals, but they're inexpensive (about $1.50/serving), pretty tasty, and relatively low-cal (about 450-500 calories per serving).
I'll also do turkey patties (which can be used to make turkey burgers, or even just eaten as is).
Better yet, you can make turkey (or beef) chili in the slow cooker - prep time is like 15minutes (brown turkey w/ seasonings) and add to slow cooker with beans, tomatoes, chilis, etc.. Keep in fridge overnight, and then just turn it on in the morning before going to work - when you come home, it's all done - and it's about 6 servings worth of food. Similar concept works with pork shoulder or any other large piece of meat that requires long and slow cooking.
Of course, this only works if you don't mind eating the same thing several times in a row.